About 30 students showed up to school wearing the wrong uniform and were told to study in the school gym.

An Education Department spokeswoman said the department was working with the school for a solution.

"We understand the school is working with students and families relating to their individual needs in relation to the implementation of the school’s uniform policy, and the students are at school today," the spokeswoman said in a statement.

Delahey mother Joanne Grey said her daughter Amy, in Year 11, was among those students because she does not have the correct school blazer.

"Amy told me she hasn't been sent home today but was sent to work in the gym,"

"I'm going to order her blazer for her this week and I intend to speak to the school about this."

The school confirmed to the Leader that no students were now being sent home if they were in the wrong uniform, but rather given classwork to complete in the gym.

Parents have estimated the cost of the new school uniform at about $400, with many questioning the need to buy a new uniform for children with less than a year's schooling left.

Principal Genevieve Simson said the school would continue to work with parents to ensure all students complied with the new code.

"We have clearly communicated the uniform policy over the last two years and there has been a long transition period to the new uniform," Ms Simson said.

"We believe that school uniforms give our students a strong sense of identity and school pride.

"We remain committed to our school uniform policy; however we recognise that some parents have not yet purchased the new uniform.

"We expect all students to be at school on Monday and we will continue to work with parents to assist them in providing the school uniform for their children."

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